Once you have had GBS you are at increased risk to have it again, but that does not mean you will.
Also, you have to decide if testing for it is even the right decision for you. You can test pos one week and be neg the next. An actual deadly newborn infection is rare, though obviously devistating.
There are also natural ways that you can deal with gbs to try to get rid of it and then retest.
You can also obtain abx for iv from a doctor (if not your own a homebirth midwife migth know who) for use at home if you wanted.
There is also the hibicleans protocal for use during labor. This has shown in a few studies to have equal outcomes to abx in regards to gbs infected babies. This is a nice option because although it is an antibacterial solution that is used to flush the vaginal area, it is not systemic flushing of bacteria like iv abx and will not effect the babe. Here in MA many or most of the midwives use this on thier moms who chose to test and have a postive outcome. Sometimes we use it for moms who have not tested or were even negative when they have prolonged rutpure of membranes.
Best of luck! Paige